PROJECT SUMMARY/ABSTRACT: Toxoplasma gondii is an important opportunistic pathogen of humans, and if a women is infected during pregnancy it can cross the placenta and result in disastrous outcomes for the developing fetus. Congenital infection in this parasite is common, but poorly understood especially at the molecular level. In this proposal we outline a focused set of experiments aimed at understanding what happens when Toxoplasma gondii encounters cells of the placenta. Our extensive preliminary data show that human placental cells respond to Toxoplasma infection by secreting chemokines (such as CCL22) known to be associated with spontaneous abortion and miscarriage. Secretion of this chemokine requires parasite invasion and does not occur after infection with the closely-related apicomplexan Neospora caninum. Our data also show that the CCL22 ?response? of placental cells is likely driven by the secretion of an as-yet unknown Toxoplasma effector into the host cell. The focus of this exploratory proposal is to use molecular genetics to identify the molecular players from both parasite and host that are required for T. gondii-induced chemokine secretion. In Aim 1 we identify T. gondii CCL22-inducing effectors using a candidate gene approach informed by an in silico screen. We also propose a backup mutagenesis screen in the event that the candidate approach fails. In Aim 2 we identify the placental host cell transcription factors required for the induction of this signal, building off of data showing that the CCL22 response to T. gondii infection is restricted to only a subset of human cell types. Aims 1 and 2 are facilitated by our discovery of a genetically tractable human cell line (THP-1) that faithfully recapitulates the CCL22 induction profile of human placental cells. Together, the CO-PD/PIs are uniquely positioned to perform the proposed studies. Boyle is a molecular parasitologist with extensive experience in identifying pathogenesis determinants using genetic and bioinformatics-based approaches, and Coyne is an expert virologist and cell biologist with extensive experience in studying pathogen/placenta interactions. In conclusion, our Aim is to exploit our complementary skill sets to characterize the outcomes of the Toxoplasma/placenta encounter at the molecular level.